1. Field of the Invention
The present invention relates to a magnetic head used in a magnetic recorder such as a floppy disk drive or the like.
2. Description of the Related Art
FIGS. 2a-2c show a structure of a conventional magnetic head, in which FIG. 2a is a plane view thereof, FIG. 2b is an enlarged view of a portion B in FIG. 2a and FIG. 2c is a diagram showing a recorded pattern on a track in a recording medium.
In FIGS. 2a and 2b, there are provided an erase gap 5 on the left and a read/write gap 6 on the right of the center of a lower part of a core 1 forming a magnetic circuit. An erasing coil 2 for generating a DC magnetic field H.sub.E upon the erase gap 5 for erasing data which have been already recorded on the recording medium is wound around a left arm of the core 1. Further, a first read/write coil 13 for generating a magnetic field H.sub.1 upon the read/write gap 6 for recording data having one polarity in the recording medium and a second read/write coil 14 for generating a magnetic field H.sub.2 in an opposite direction to the magnetic field HI for recording data having a polarity opposite to the above-mentioned polarity are wound around a right arm of the core 1. The first read/write coil 13 and the second read/write coil 14 have the same number of turns.
In a conventional magnetic head having such a structure as described above, in the case of an antecedent erase system, an electric current flows in the erasing coil 2 so as to erase the data, which have already been recorded on the medium, by saturating the medium with the DC magnetic field H.sub.E upon the erase gap 5. Next, the erased part of the medium proceeds to the read/write gap 6, and is magnetized to the right or to the left by the magnetic field HI or the magnetic field H.sub.2 generated by an electric current applied to either one of the first read/write coil 13 or the second read/write coil 14. A reference numeral 17 in FIG. 2c represents a recorded pattern on a track in the recording medium. Since the moving direction of the medium is to the right, recording is made gradually from the right portion to the left in the figure.
In the conventional magnetic head described above, however, when the antecedent erase system is adopted, the recording magnetic field is affected by a bias magnetic field H.sub.3 which is leakage from the DC magnetic field H.sub.E generated by the erase current to the read/write gap 6, wherein the recording magnetic field to the right becomes stronger by being added with the bias magnetic field H.sub.3 and the recording magnetic field to the left becomes weaker by being deducted by the bias magnetic field H.sub.3. Therefore, there has been such a problem that imbalance due to the direction, i.e., asymmetry is produced in the intensity of magnetization recorded on the recording medium, and an error rate is increased at a time of reading the recorded data unless an asymmetrical circuit for correcting the imbalance is used.